Production of fuel oils

ABSTRACT

FUEL OILS OR FUEL OIL COMPONENTS ARE PRODUCED FROM WAXY ATMOSPHERE RESIDUES BY VACUUM DISTILLING THE RESIDUE TO GIVE A WAX DISTILLATE FRACTION AND A VACUUM RESIDUE, SELECTIVELY DEWAXING THE WAX DISTILLATE FRACTION AND REBLENDING AT LEAST A PORTION OF THE DEWAXED WAX DISTILLATE FRACTION WITH AT LEAST A PORTION OF THE VACUUM RESIDUE. THE PROCESS IS PARTICULARLY SUITABLE FOR ATMOSPHERIC RESIDUES WITH 15-35% WT. WAX. THE PREFERRED SELECTIVE DEWAXING PROCESS IS CATALYTIC, INVOLVING PASSING THE WAX DISTILLATE WITH HYDROGEN OVER A CATALYST OF A GROUP VIA AND/OR GROUP VIII HYDROGENATING COMPONENT INCORPORATED WITH MORDENITE OF REDUCED ALKALI METAL CONTENT. THE MORDENITE IS PREFERABLY DECATIONISED AND HAS A SIO2:A12O3 RATIO OF AT LEAST 14:1. THE DEWAXING CONDITIONS MAY BE 450-950*F., 250-3000 P.S.I.G., 0.2-20 V./V./HR. AND 1000-3000 S.C.F. OF H2/B.

United States atcnt US. Cl. 208-28 7 Claims ABSTRACT OF THE DISCLOSURE Fuel oils or fuel oil components are produced from waxy atmospheric residues by vacuum distilling the residue to give a wax distillate fraction and a vacuum residue, selectively dewaxing the wax distillate fraction and reblending at least a portion of the dewaxed wax distillate fraction with at least a portion of the vacuum residue. The process is particularly suitable for atmospheric residues with 1535% wt. wax. The preferred selective dewaxing process is catalytic, involving passing the wax distillate with hydrogen over a catalyst of a Group VIa and/ or Group VIII hydrogenating component incorporated with mordenite of reduced alkali metal content. The mordenite is preferably decationised and has a SiO :Al O ratio of at least 14:1. The dewaxing conditions may be 450-950 F, 250-3000 p.s.i.g., 0.2-20 v./v./hr. and 1000-3000 s.c.f. of H /B.

This invention relates to the production of fuel oils from waxy residues.

Fuel oils are heavy petroleum fractions and usually atmospheric residues diluted with lower boiling fractions, where necessary, to reduce viscosity. Their composition is not critical as such except in so far as the composition affects the handling and storage of the oils. Currently most fuel oils are required to meet a maximum pour point limit between and 70 F. depending on the viscosity grade which is usually within the range 200 to 3500 Redwood No. 1 seconds at 100 F. (13 to 93 est. at 170 F.). This means that atmospheric residues from certain waxy crude oils cannot be used directly as fuel oils. This is regrettable since these waxy crudes often have low sulphur contents, which is a desirable property in view of the current emphasis on reducing atmospheric pollution.

A method of making residues from waxy crude oils suitable for use as fuel oils or components of fuel oils is thus potentially useful. Since the high pour points of the waxy crude oils are due to their high wax contents, dewaxing would be one such method, but dewaxing the whole of an atmospheric residue would be costly.

It has now been found that only a part of an atmospheric residue from a waxy crude oil has to be dewaxed in order to produce a satisfactory fuel oil.

According to the present invention, therefore, a process for the production of fuel oils or fuel oil components comprises distilling an atmospheric residue, containing at least 5% wt. of wax and having an initial boiling point within the range 320370 C., under vacuum to give a wax distillate fraction having an initial boiling point of 320-370 C. and a final boiling point of 500- 600 C. and vacuum residue constituting the remainder of the atmospheric residue, selectively dewaxing the wax distillate cut to reduce the wax content of the wax distillate by at least 4% wt. and blending at least a proportion of the dewaxed wax distillate with at least a ice proportion of the vacuum residue to give fuel oil or a fuel oil component.

The wax distillate is selectively dewaxed so that the desirable lower-boiling, low viscosity, components are not unnecessarily destroyed. The dewaxing may thus be a solvent dewaxing process (using, for example, as solvents chlorinated hydrocarbons, lower alkyl ketones with or without an aromatic such as benzene or toluene, and lower boiling alkanes) or urea adduction. Preferably, however, the dewaxing is a catalytic dewaxing over a catalyst based on a particular zeolite, mordenite, which has the unusual characteristic of selectively cracking waxy hydrocarbons. Thus the process may be similar to that described and claimed in U.K. patent specification No. 1,088,933 and the complete specification of U.K. patent application No. 53,783/66. (Now U.K. patent specification No. 1,134,014.)

The wax distillate may therefore be passed at elevated temperature and pressure and in the presence of hydrogen over a catalyst comprising one or more hydrogenating components selected from Groups VIa and VIII of the Periodic Table incorporated with a crystalline mordenite of reduced alkali metal content.

The term crystalline mordenite of reduced alkali metal content means, preferably, a mordenite with an alkali metal content of less than 3% wt. The deficiency of alkali metal cations can be made up with other metal cations for example Group II metal cations, particularly magnesium, or rare earth metal cations. Preferably however the mordenite is a decationized mordenite, which means a mordenite having a deficiency of metal cations. An alternative term in the art is hydrogen mordenite, since it is assumed that when metal cations are removed they are replaced by hydrogen ions. However, since it is not possible to detect the presence of hydrogen ions in zeolites, the precise structure remains in doubt. A cation deficiency can, on the other hand, be readily measured by analysis of the metallic elements present in the zeolite.

Natural or freshly prepared synthetic mordenite has the formula:

lMe 2 o muo s-11 si0 .XH20

where Me is a metal cation, 12 is the valency of the cation and X is variable between nil and 7 depending on the thermal history of the sample. Me is commonly sodium and in one common form of decationisation sodium mordenite is base exchanged with ammonium cations. The ammonium form is then heated to drive off ammonia, leaving behind the hydrogen form or decationised mordenite. According to the second method the mordenite may be treated with a mineral acid, for example hydrochloric or sulphuric acid, in order directly to decationise the mordenite. A combination of acid treatment and ammonium treatment can also be used.

Preferably the decationized mordenite used in the present invention has a higher than normal silicazalumina ratio of at least 14:1. In specific examples ratios of as :1 have been obtained and a practical upper limit may thus be :1. Particularly preferred silica:alumina ratios are in the range 16:1 to 50:1.

It has been found that certain decationization treatments remove aluminium as well as the expected metal cations and desirably therefore the mordenite used in the present invention having a higher than normal silicazalumina ratio is obtained by treatment of a metal cationcontaining mordenite, particularly sodium mordenite, with a trong acid, for example sulphuric or hydrochloric acid, of from 550% wt. strength and preferably from 10 to 20% wt. strength. A single treatment or two or more 3 successive treatments may be given with acids of the strengths stated above.

A convenient method of treatment is to treat the mordenite with acid under reflux for a period of 2-12 hours.

In the decationized mordenite the metal cation content, for example the sodium cation contact, should be less than 2% wt. of the mordenite and preferably less than 1.5% wt. of the mordenite.

It should be emphized that mordenites with higher than normal silicazalumina ratios-retain the crystal structure of mordenite and are not significantly altered in terms of physical strength, stability or crystallinity.

The hydrogenating component is preferably a platinum group metal, particularly platinum or palladium, and it is preferably added by ion-exchange. Preferably the mordenite is aged in water before adding the platinum group metal as described in the specification of U.K. application No. 4,421/68. The amount of the platinum group metal is preferably within the range 0.01 to 10% wt., particularly 0.1 to wt. However, iron group metals, particularly nickel, may also give useful results. Mixtures of certain Group VI and VIII metals and compounds may also be used, e. g. cobalt and molybdenum.

The catalyst is preferably calcined at for example 250- 600 C. before use to remove any water and to eliminate any ligands attached to the hydrogenation component.

Sulphur and nitrogen compounds, if present, do not have to be removed before the catalytic dewaxing, but it may be desirable to scrub recycle gases to remove any hydrogen sulphide and ammonia produced.

Suitable process conditions include a temperature within the range 450-950 R, (232-510" C.) preferably 500- 850 F., (260454 C.) a pressure within the range 250- 3000 p.s.i.g, preferable 500-2500 p.s.i.g, a space velocity between 0.2-20.0 -v./v./hr., preferably 0.4-8.0 v./v./hr., and a gas rate of %-30,000 s.c.f. of hydrogen/B preferably 5000-15,000 s.c.f. of hydrogen/ B. The precise process conditions in any given situation will depend on the wax content of the feedstock and the extent of wax destruction required.

The wax is converted mainly to C and C parafiins with some C and only minor amounts of higher hydrocarbons. Separation of the conversion products from the main reaction effluent which is unconverted Wax distillate can thus be a simple stripping operation.

The wax content as specified in the present invention is defined as the amount of material precipitated from methylene chloride solution at F. In this method a known weight of residue is dissolved in hot methylene chloride in a flask, the ratio of methylene chloride to residue being 10:1, (or higher in the case of very high wax content residues). The solution of residue in methylene chloride is then cooled to 25 F. and held at this temperature for minutes. The precipitated wax is separated by filtration, washed with methylene chloride at -25 F. until the filtrate is colourless. redissolved in petroleum ether, transferred to the original flask and weighed after evaporation of the petroleum ether. The wax content isgiven as percentage by weight on the original residue. If the residue to be tested for wax content contains asphaltic material it may be desirable to separate the asphalt before testing. The pour point of the fuel oil is determined by the Institute of Petroleum Test No. IP/ 15. The actual pour point of the finished fuel oil which is required may vary according to the proposed use but in general commercial fuel oil pour points lie in the range of 0 F. to 70 F. Required viscosities of fuel oils within these pour point ranges will normally be 200-3500 Redwood No. 1 seconds at 100 F. (13-90 cs. at 170 F).

While the present invention may be used with atmospheric residues having as low a wax content as 5% wt. it is particularly suitable for use with feedstocks having a high wax content (i.e. 1535% wt.). As stated earlier. certain high wax content atmospheric residues have low sulphur content of less than 1% wt. and these are par- 4- ticularly preferred feedstocks. With the 15-35% wt. wax feedstocks the reduction in wax content of the wax distillate is preferably at least 10% Wt. e.g. l0-25% wt.

Examples of high wax content, low sulphur content atmospheric residues are residues derived from certain Libyan and Nigerian crude oils. The pour points of these residues may be from to F. Splitting the residue gives a wax distillate with a pour point within the range 80 to F. and a vacuum residue with a poor point from 80 to 160 F. Dewaxing of the wax distillate according to the present invention reduces the pour point to 10-60 F.

Other components may also be blended with these components depending on the precise grade of fuel oil required. These other components may be high wax content untreated atmospheric residue, atmospheric or vacuum residues derived from other crude oils or gas oil from any convenient source.

The invention is illustrated by the following examples.

EXAMPLE 1 An atmospheric residue derived from a Libyan crude oil was distilled under vacuum to give a wax distillate fraction and a vacuum residue. Inspection data on the three fractions are given in Table 1 below.

TABLE 1 Atmos- Wax pheric distil- Vacuum residue late residue Initial boiling point, C 304 305 475 Final boiling point, C l 625 2 573 8 596 Pour point, F 110 120 155 Viscosity, cs. at 210 F 22. 90 5. 19 3832 Sulphur, percent wt 0. 38 0.25 0. 5

Nitrogen, percent wt 0. 0.018 0. 006 0. 037

Wax content, percent wt 24. 3 26. 7 l9. 9 Yield on atmospheric residue, percent 1 71% vol. yield.

2 98% vol. yield.

3 16% vol. yield.

The wax distillate was catalytically dewaxed over a catalyst of platinum on hydrogen mordenite having the following inspection data The run was continued for 370 hours and the products obtained during the periods 44-132 hours on stream and 242-370 hours on stream were stripped of material boiling below C. and analysed with the results shown in Table 2 below.

TABLE 2 4 1-132 242-370 HOS HOS Yield, percent. wt 63. 9 Pour point, F. 40 Wax content, percent w 5. 6 5. 5 Viscosity, cs. at 122 F 38. 93 31. 26 Sulphur. percent wt 0. 40 0. 37 Nitrogen, percent Wt 0. 099 0. 094

The product from 44-132 HOS was called Product A and that from 242-370 HOS, Product B.

Portions of Products A and B were blended with portions of the vacuum residue of Table l. The proportions used and the results obtained are given in Table 3.

TABLE 3 TABLE 6.-l,500 SECONDS FUEL OIL Blend N o 1 2 8 4 Composition:

Product A, percent wt 23. 9 24. 6 Product A (pour point 40 F.), percent wt 50. 7 75 Product B, percent wt 25. 6 Product B (pour point 30 F.), percent wt. 51. 1 75 Libyan vacuum residue, percent wt 23. 3 23. 9 24. 5 Vacuum residue (pour point 155 F.) wt- 49. 3 25 48. 9 25 5 Middle East atmospheric residue, percent Pour point of blend, F 35 wt 39. 6 38. 40. 3 Viscosity of blend. cs. at 170 F 141. 9 39. 7 93. 2 36. 4 Diluent 0, percent wt 13. 2 9. 6 Diluent D, percent wt 13. 0 Analytical data:

Specific gravity at 60 F./60 F 0. 939 0. 949 0. 9405 Total sulphur content, percent wt 1. 83 1. 92 1.82 10 Flash point (PMC), F 245 265 152 Kinematic Viscosity at 100 F., cst. 334. 9 381. 9 378.6 Kinematic viscosity at 122 F., cst 159. 1 169. 0 174. 5 Blends 1 and 3 were blends in the proportion of the Pour point 24 hours after blending) F- 50 45 45 atmospheric residue after allowance had been made for 33; 332% 33;: 3&2; gigggigggw g :2 i8 28 the conversion of the wax in the wax distillate to lighter Pour point (14 days after blending),: F 40 4o 45 material and it will be seen that the pour point of the 15 ,gggg igiggg ggv e blending), f0 'ii blend was the same as that of the dewaxed wax distillate despite the fact that the blend contained nearly 50% of vacuum residue of 155 F. pour point. Blends 2 and 4 used only part of the vacuum residue and gave a blend with a lower pour point than either component.

EXAMPLE 2 Products A, B and the vacuum residue from Example 1 were used together with other components to give fuel oils meetings current commercial specifications. Inspec- S tron data on the other components are as shown 1n Table TABLE ECONDS FUEL OIL 4 below. Composition:

Product A, percent wt- 20.3 33. 8 Product B, percent wt 20. 7 Libyan vacuum residue, percent w 19. 7 19. 9 11. 3 Middle East atmospheric residue,perccnt wt 54.2 Middle East vacuum residue, percent wt 40. 8 41. 6 Diluent 0, percent Wt 5. 8 18. 6 13. 3 TABLE 4 Analytical data:

Specific gravity at 60 F./60 F 0.9515 0.949 0.9495 Middl Total sulphur content, percent wt 2. 45 2. 44 2. 38 East Middle Gas Gas F ash point (PMQ), F 265 214 250 gtmos- E t 011 on Kinematic viscosity at 100 F, cst 716. 6 698. 9 673. 6 pheric vacuum diluent diluent Kinematic v scosity at 1 F, cst 285. 9 297. 5 288. 7 r id r id (J D Pour point (24 hours after blending), F. 45 25 25 Pour point (3 days after blending), F 45 20 20 Specific gravity at 50 F./60 F- 0. 9555 1. 020 0. e420 0. 9210 Pour po nt (7 days ter ble e). 45 2o 20 Sulphur content, percent wt 4. 17 5. 22 1.03 1. 51 Pour poi t y after b e ding), F 45 20 20 Viscosity, cs. at 100 1,093 3. 62 3.16 P n t d after s), 45 0 15 Viscosity, cs. at 170 F 4, 903 Thermal stabihty Stable Viscosity, cs. at 210 F 40. 54 974. 3 Pour point, F 100 5 0 Wax content, percent wt 10. 1 8. 0 Flash point, F 204 206 These components were blended to give fuel oils of 650 seconds, 1500 seconds and 3500 seconds viscosity respectively (Redwood No. 1 seconds at 100 F.). Th propor- T e tables above show that fuel oils meeting commertions used and the results obtained are shown in Tables 61211 speclficatlons prepared Wlth, 111 the P of the 5, 6 and 7' 3500 seconds fuel 011, a cons1derab1e margln on pour point. The tables also show that the fuel oils were thermally stable and that there was no pour point drift with time.

We claim: 55 1. A process for the production of fuel oils or fuel TABLE 5.650 SECONDS FUEL OIL oil components comprising: distilling an atmospheric Composition: residue, containing at least 5% wt. of wax and having an Product A, ercent wt 34.5 36.8 initial boiling point within the range 320370 C., under figggg fi ggg ggggvacuum to give a wax distillate fraction having an initial wt 20.2 21.5 11.5 12. boiling point of 320370 C. and a final boiling point of giji fi gij jf j fi 3&7 3m 3 370 500-600 C. and to give a vacuum residue constituting Di t C percentwt 19.9 14.3 m the remainder of the atmospheric residue; selectively cat- 3.239533 M alytically dewaxing the wax distillate fraction to reduce p f g a y fifil -/6 0. 93% 0 94 25 0. 92 0. 933 the wax content of the wax distillate fraction by at least ii i fi ii t 4% wt. by passing it, together with hydrogen, at a tem- Kin mati vis i y 139: 1, 5 155.36 3 perature of 450-950 F., a pressure of 250-3000 p.s.i.g., 533: 333?gi gig g, fif- 8 8 8 a space velocity of 0.220.0 v./v./hr. and a hydrogen gas s), 35 40 25 30 rate of 1000-30,000 s.c.f. of hydrogen/B over a catalyst 35 30 25 25 comprising one or more hydrogenating components select- Pgur p t y after blending), 30 30 30 25 ed from Groups VIa and VIII of the Periodic Table in- Pom 555g igdggg'gf 'gg 5 5m; corporated with a crystalline mordenite of reduced alkali s 30 30 35 25 metal content; and blending at least a proportion of the ;,1; f2 30 30 35 20 dewaxed wax distillate fraction with at least a proportion Th ma st y Stable of the vacuum residue to give a fuel oil or a fuel oil ASTM D-1561. component.

2. A process as claimed in claim 1 wherein the atmospheric residue feedstock has a Wax content of 15 to 35% wt.

3. A process as claimed in claim 2 wherein the reduction in Wax content of the wax distillate is at least 10% wt.

4. A process as claimed in claim 1, wherein the dewaxing is carried out at a hydrogen temperature of 500- 850 F., a pressure of 5002500 p.s.i.g., a space velocity of 0.4-8.0 v./v./hr. and a gas rate of 5000-15,000 s.c.f. of hydrogen/B,

5. A process as claimed in claim 1 wherein the mordenite is a decationised mordenite having a metal cation content of less than 2% wt.

' 6. A process as claimed in claim 1 wherein the mordenite has a silicazalumina ratio of at least 14: 1.

7. A process as claimed in claim 6 wherein the mordenite has a silicazalumina ratio of from 16:1 to 50:1.

References Cited UNITED STATES PATENTS 2/1966 Chen 208-15 3/1966 Kimberlin et a1 208-28 8/ 1967 Rigney et a1. 208-28 9/1968 Tung et al. 208-28 FOREIGN PATENTS 6/1965 Great Britain 208-15 4/1966 Great Britain 208-15 10/1967 Great Britain 208-28 U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION fi'q I PatentNo. 3511M Dated Aprll 7 1 Robert William Aitken and Bernard Whiting Burhidge Inventor-(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 32, for "3000" read --3000O--;

Column 3, line 75 or "content read --conte-nts--;

Column 2 line 9, for "poor" read --pour--; n

Column 7, line 9, for "a gas" read -a hydrogen gas-n Signed and sealed this 26th day of October 1971.

(SEAL) Attest:

EDWARD MELETQHER, JR. ROBERT GOTTSCHALK Attesting Offlcer Acting Commissioner of Paton 

